[JesseK]

I may be that your tubing is hooked into the valve incorrectly, therefore the valve does not have enough working pressure to work.

For us, the input is "1"
"3" and "4" go to the pneumatic cyllinder.

You never know, someone may unhooked it then accidentally hooked back up incorrectly. Charge the pneumatic system to 60 psi, then test. If not, then try a new spike.